Busy back circuits



I. F. TOOMEY.

BUSY BACK CIRCUITS. APPUCKTION FILED APR. 1. m9.

Patented June 14, 1921.

2 SHEETS-SHEET I.

ATTORNEY IN VEN TOR. J1? Yamy J. F. TOOMEY.

BUSY BACK cmcuns.

APPLICATION FILED APR. 11 1919 Patented June 14, 1921.-

2 SHEETS-SHEET 2.

A TTORNE'Y v INVENTOR. T 1E 750mg;

UNITED STATES JOHN TOOMEY, OF NEW YORK,

PATENT OFFICE.

AMERICAN TELEPHONE AN D BUSY BACK CIRCUITS.

Application filed April 1,

To all whom it may concern:

Be it known that I, JOHN F. TOOMEY, residing at New York, in the county of New York and State of New York, have invented certain Improvements in Busy Back Circuits, of which the following is a specifica tion.

This invention relates to telephone systems and more particularly to means for indicating when a called line is busy.

The invention consists in the provision of improved means whereby the busy condition of a called subscribers line dicated in the case of a local call ator at the oiiice wherein or in the case of a long operator at the incomin toll switchboard. provision of improved means for transmitting an audible as well as visual busy signal to such an operator for the purpose of mak ing the signal more easily distinguishable. Other and further features of the invention will be clear from the detailed description to be given later.

A telephone call between subscribers lines associated with different central offices or exchanges, is completed by means of trunk circuits interconnecting such offices. The operator at the oflice nates communicates with the operator at the exchange of the called subscriber and then connects her cord circuit with a suitable trunk circuit designated by the latter operator, which trunk circuit is then connected with the line of the called subscriber. In the case of a long distance or toll call, the connection is completed in a similar manner over toll switching trunks. of the called subscriber be found to be busy or in use there is providec board of the central ofiice associated with the called. subscribers line a set of busy jacks into which the local trunk circuit may be inserted and an additional set of busy jacks into which the toll switching trunk may be inserted in the case of a toll call. Thesebusy jacks are associated with busy back circuits which include apparatus for intermittently closing circuits associated with the trunk circuits and the cord circuits of the calling operator whereby the supervisory signals associated with the calling operators cord circuit will be caused to flash and inform the operator of the busy condition of to theoperthe call originated distance call to the g long distance or Specification of Letters Patent.

may be in It further consists in the.

wherein the call origi Should the line i at the switch-.

trated modifications Patented June 14, 1921. 1919. Serial No. 286.660.

the called line. In former arrangements of this character two separate sets of busy acks were provided, one set suitable for use with local trunk'circuits and the other set suitable for use with toll switching trunks. arrangements have been found tobe unreliable should a local trunk e inserted in one of the jacks adapted for a toll switching trunk or should a toll switching trunk be inserted in one of the jackssuitable for a local trunk. F urthermore if a defective local trunk or defective toll trunk is connected with former types of busy back circuits, the busy back signals applied-to other lines connected to the busy ack circuit would fail until the defective trunks are removed. Also in oiiices having machine ringing trunks, a considerable amount of interference is noted when a machine ringing trunk is plugged into the busy back circuit. In order to eliminate such interference and to do away with the above mentioned difiiculties, the busy back circuit embodied in this invention has been provided. i

In the busy back circuit of this invention but one set of jacks is provided adapted to be used with either local trunk circuits or toll switching trunks. When a trunk is associated with one of the jacks, relay means connected to the sleeve circuits of all the jacks will operate and close a circuit including additional relay means and an interrupting apparatus thereby causing these other relay means to functionintermittently. The operation of these relay means serves to complete individual busysignaling circuits for each oneof the jacks. Additional means are provided for superimposing an audible signal on the busy back circuit as will appear-more fully in the detailed de scription of the operation.

-In the drawing, Figures 1 and 2 when taken together illustrate a circuit diagram of'a preferred form of the arrangements of the'invention. In Figs. 3 and 4 are illus thereof.

In Fig. 1 are illustrated types of cord circuits and trunk circuits suitable for completing local and long distance calls. These types of cord circuits and trunk circuits are Well known in the art and only portions thereof essential for the operation of this inventionare illustrated. A local cord circuit l is shown terminating into plugs P and P Associated with ring conductor of cord circuit 1 is the supervisory relay 5 adapted to control the supervisory lamp 6. The local cord circuit 1 may be associated with the local trunk circuit 2 by means of the jack J Included in the trunk circuit 2 is the repeating coil 9. Associated with one of the windings thereof is the relay 7 having two windings, one of high and'one of low resistance. Associated with the. talking conductors of trunk 2 is thesupervisory relay 8 which serves to close a short circuit about the high resistance winding of relay 7 and thus controls the operation of relay 5. The relay 7 controls the usual type of guard or disconnect signal such as the lamp 11 associated with'the sleeve relay 10 of the plug P For completing a long distance call, the

' toll cord circuitB is employed. Included 'in a bridge across the talking conductors of toll cord 3 are the high impedance windings 13 and'the supervisory relay 14 which controls the signal lamp 15. A toll switching trunk 4 is shown including the repeating coil 16 associated with one of the windings of which is the relay 18 and a source or current 19 which serves to operate relays 1 1 and 18.- Associated with the other winding of repeating coil 16 is the supervisory relay 20 and the relay 17 which, in turn, controls the relay 14.

In Fig. 2 is shown a preferred form of the busy back circuit embodied in this invention. Associated with the sleeve conductors of the jacks J,,. J, J J,,, J, and J,, is the relay 53 which operates whenever a trunk is associated with one of said jacks. Included in the sleeve and ring conductors associated with the jacks are resistance ele- 'ments adapted to simulate a subscribers line.

The operation of relay 53 serves to complete circuits for relays 56 and 57 which circuits include the interrupting apparatus 5 1. The relays56 and 57 serve to complete individual busy signal circuits for each of the jacks as will be pointed out more fully in the description of the operation.

In Figs. 3 and 1 are illustrated'modifications of the arrangement shown in Fig. '2. In Fig. 3 a transformer 32 is illustrated with which is associated an interrupter33 and a source of'current. The transformer 32 is associated in common with the ring conductors of all of the jacks of the busy back circuit and .provides'a means for transmitting an audible busy signal over lines connected therewith. In the Fig. 4 an audible busy signal is impressed on the busy 7 back circuit by means of the transformer 14 associated with a conductor connected to the tip contacts of all the jacks. Associated with transformer H are the interrupters 15 and 7 9 which are adapted to function at different speeds.

The invention may now be more fully unthe trunk circuit 2,

derstood from the following description of its operation. In the case of-a. local call, if the operator finds that the subscriber desires a connection with a line associated with another central office, she communicates with the operator at such oilice by means of a call wire circuit and is informed by the latter operator of a suitable trunk circuit, such as with which to associate her cord circuit, such asthe cord circuit 1. When the cord circuit 1 is connected with trunk 2 by means of the plug P, being inserted in jack J,, the following circuit is completed; from ground, sleeve conductor of jack 3,, sleeve contacts of jack J, and plug P.,, sleeve conductor of plug P resistance 62, conductor 6%, filament of lamp 6, to battery. The closing ofthis circuit will operate lamp 6; The insertion of plug I into jack J, also closes the following circuit: from one side of battery 65, tip conductor of cord 1, tip contacts of plug I, and jack J tip conductor of trunk 2, upper left hand winding of coil 9, conductor 66, high and low resistance windings of relay "7, conductor 67, lower left hand winding of coil 9, ring conductor of trunk 2, ring contacts of jack J, and plug P ring conductor of cord 1, winding of relay 5, ring conductor of cord 1, to the opposite side of battery 65. The upper winding of relay 7, however, is of sififiiciently high resistance so that the closing of this circuit will not operate supervisory relay 5. The local call is completed by the operator at the central ofiice, with which the called subscribers line is associated, insert ing the plug'P, of the trunk 2 into the jack of the callel subscribers line. Upon the operation of relay 7, a circuit is completed from ground and battery, filament of lam 11, contact and armature of relay Karinature and back contact of relay 10, lower winding of relay 10 to ground. 'The closing of this circuit will light lamp 11 but will not operate relay 10 at this time as the lower winding of relay 10 is marginal and will prevent the operation of the relay at this time. lVhen the plug P is inserted in the jack of the called line or the busy back jack, a circuit is completed from ground in the sleeve circuit of the jack sleeve, circuit of the plug I,,, upperwinding of relay 10 to battery and ground. The closing of this circuit will operate relay 10 and the circuit for lamp 11 will now be completed as follows: from ground to battery, filament of lamp 11, contact and armature of relay 7, armature and front contact of relay 10 through a low resistance to battery and ground. I The circuit for the lamp 11 will be completed as de scribed instead of through the upper winding of relay 10, because the resistance in said circuit is lower than that of the resistance of the upper winding of relay 10 and acts as a shunt therefor, As battery is found at both ends of this circuit, the lamp 11 will be extinguished at this point. lVhen the called subscriber responds, the following circuit is closed: from ground, upper right hand winding of coil 9, tip conductor of trunk 2, tip contact of plug P out over the subscribers line, through the subscribers substation, back over the subscribers line, ring contact of plug P ring conductor of trunk 2, winding of relay 8, ring conductor of trunk 2, lo er right hand winding of coil 9, to battery 70. The closing of this circuit will energize relay 8 which will pull up its armature and close a short circuit ineluding conductors 68 and 69 about the high resistance winding of relay 7, so that the circuit formerly closed through relay 5 will no longer include the high resistance winding of relay 7, and relay 5 will now operate. The operation of relay 5 closes a circuit from battery, filament of lamp 6, conductor 64, resistance 63, armature and conta t of relay 5, to battery. As resistance 63 is of smaller value than resistance 62, the closing of this circuit will provide battery at both ends of the circuit for lamp 6 and accordingly extinguish signal lamp 6 and thus inform the operator that the connection has been completed.

Should the line of the called subscriber be busy, the operator at the central office with which the subscriber is associated-will insert the plug P of trunk 2 into one of the jacks of the busy back apparatus 51, such for example as the jack J thereby closing the following circuit: from battery, filament of disconnect signal lamp l1, winding of relay 10, sleeve conductor of plug P sleeve contacts of plug P and jack J sleeve conductor of jack J conductor 52, winding of relay 53, to ground. This will operate relay 53 and close the following circuit: from battery, winding of relay 56, conductors 59 and 60, contact and armature of relay 53, con-- duetor 55, interrupter 54, to ground. This will energize relay 56 and close the following'circuit: from ground, conductor 61, conductor 71, contact and armature of relay 5 6, conductor 72, ring contacts of jack J and plug P ring conductor of trunk 2,-winding of relay 8, ring conductor of trunk 2, lower right hand winding of coil 9, to battery 70.

he closing of this circuit will operate relay 8 which in a manner previously pointed out will short circuit the high resistance winding of relay 7 and cause the operation of supervisory relay 5 in cord circuit 1 which in turn and as previously pointed out will extinguish the signal lamp 6. However as the previously traced circuit including the winding of relay 56 includes the interrupter 54:, the relay 56 will function intermittently. Accordingly, the relays 8 and 5 will be caused to operate intermittently and the signal 6 will be caused to flash intermittently, tl ereby informing the operator that the called line is busy. Upon being thus informed of the busy condition of the called line the operator removes the plug P from the jack J thereby opening the previously described circuit through relay 7 and deenergizing relay 7. The dele'nergization or" relay 7 serves to open the usual circuit controlled thcreby and to cause the functioning of the usual disconnect signal 11, whereupon the trunk 2 may be disassociated from the busy jack. is the operation would be substantially the .anie as described were a connection to be made with any of the other jacks of the busy back circuit 51, such as jacks J J 5 J,,,, or 5 no "further description thereof will be given.

he operation, when a trunlr circuit such as the trunk 2 is associated with a busy bacl: circuit such as the circuit 49 illustrated in Fig. 3, is as follows: The plug P is inserted in one of the jacks such as the jack J and the following circuit is closed: from battery, filament of lamp 11, winding of relay l0, sleeve conductor plug it, and jacl: J conductors 46 and 4:7, winding of relay l8'to ground. This operates relay lS, thereby closing the following circuit: irom buttery, winding of relay 26, conductor 25, contact and armature of rela d8, conductor 'nterrupting apparatus 23, to ground. ing of this circuit will e.- I thereby closing the "following ground, winding of ransi" ductors 29, 39 and 73,

7 circuit: from :ner 32, conare and conta 74, ring cont-i ts of ring conductor of trunl;

ring conductor oi d winding of coil 9,

of relay 26, conductor jack J, and plug 2, winding of rel trunl: 2, low *cr 1 to battery ner as prev ly poT out relay 5 and the su- As the circuit, includ I f g of relay 26, includes the interrupter .ie relay 26 will function intern" tly. Accordingly the relays 8 a inction i i'ei tently and the sunerrisory signal lamp 6 be caused to iia manner pre pointed out, of the busy con audible signal will mitted to the sulx as follows: The *3, together with t l a current of audible freq einitted as follows: from llllll conductors 29., 30 and 7S, tact of relay I 6. conductor 7%, ring contacts of iack J, c I ring conductor of trunk 2, ri of transformer 9. tip conductor 2, tip contacts of plug P and jack ground. This n this circuit filament of will then be transmitted through transformer 9, over the talking conductors of trunk 2 and cord circuit 1 in the usualmanner. As the operation would be substantially the same if the trunk circuit 2 were associated with any of the other jacks of busy back circuit 49, no further description thereof will be given.

If a trunk circuit such as the circuit 2 should be associated with the form of busy back circuit, as illustrated in Fig. 4, the operation would be as follows: The plug P would be inserted in one of the jacks of circuit 50, such as the jack J,,, and the following circuit would be closed: from battery, lamp 11, winding of relay 10, sleeve conductor of plug P sleeve contacts of plug P, and jack J sleeve conductor of jack J conductors 34 and 35, winding of relay 36, to ground. This will operate relay 36 and close the following circuit: from battery, winding of relay 39, conductor 38, contact and armature of relay 36, conductor 42, interrupting apparatus 37, to ground. The closing of this circuit will operate relay 39, thereby closing the following circuit: from ground, conductors 76 and 77, armature and contact of relay 39, conductor 78, ring contacts of jack J and plug 1 ring conductor of trunk 2, winding of relay 8, ring conductor of trunk 2, lower right hand winding of coil 9, to battery 70. The closing of this circuit will operate the relay 8 which in the same manner as previously pointed out will operate the relay 5 and the supervisory signal 6. vAs the circuit controlling relay 39 includes the interrupting apparatus 37, the relay 39 will operate intermittently. According] y, the relays 8 and 5 will operate iiitermittently and the supervisory signal 6 will be caused to flash, thereby informing the operator of the busy condition of the called line. -At the same time an audible signal will be transmitted to the subscriber and to the operators telephone set associated with cord circuit 1 in the following manner: Associated with the conductor 43, connected in common to the tip contacts of all of the jacks of circuit 50, is the transformer 44. Associated with one winding of transformer 44 is the interrupter 79 and a source of current. Associated with the other winding of transformer 44 is the interrupter 45 and a source of current. The interrupters 45 and 7 9 are arranged to function at different speeds. lVith such an arrangement of interrupters and the source of current together with the inclusion of a condenser in the circuit, a certain distinctive tone, which is easily distinguishable from other tones and of a desirable quality for the purpose for which it is intended, will be produced and may be transmitted over thetrunk lines and circuits connected thereto. By this arrangement a current of audible frequency will be transmitted from transformer 44 as follows: over conductor 43, tip contacts of jack J and plug P tip conductor of trunk 2, right hand winding of transformer 9, to ground. This current of audible frequency will then be transmitted by means of transformer 9 over the talking conductors of the trunk 2 and the cord circuit manner.

In the case of a long distance or toll call, the plug P of the toll cord circuit 3 is associated with the incoming long distance line. If the operator finds that a connection is desired with a line associated with another central office, she communicates with the operator at such ofiice by means of a call-wire circuit and is informed by the latter operator of a suitable toll switching trunk circuit, such as the toll switching trunk 4, with which to associate tl e toll cord 3. When the toll cord 3 is associated with the toll switching trunk 4 by means of the plug P being inserted in the jack J the following circuit is closed: from ground, upper winding of relay 18, conductors and 81, upper left hand winding of transformer 16, tip conductor of trunk 4, tip contacts of jack J and plug P tip conductor of cord 3, .conductor 82,high impedance winding 13, winding of relay 14, high impedance winding 13, conductor 83, ring conductor of cord 1,-ring contacts of plug P, and jack J ring conductor of trunk 4, conductors 84 and 85, lower winding of relay 18, to battery 19 and ground. The closing of this circuit will energize relay 18. The energization of relay 18 will cause 1 in the usual of lamp 22, armature and contact of relay 21, lower winding of relay 17 conductor 88,

contact and armature of relay 18, to ground.

the following circuit to be closed: from ground and battery, filament scribers line is associated will now insert of the toll switching trunk 4 into the jack of the called subscribers line, thereby completing the connection. 'However, if the called subscribers line is busy, the operator will insert the plug P, in one of the jacks of the busy back circuit 51. illustrated in Fig. 2, such, for example. as the jack J When the plug P is inserted in the jack J the following circuit is closed: from ground and battery, winding of relay 21, sleeve conductor of plug P sleeve contacts of. plug P and jack J sleeve conductor of jack J conductor 52,

the plug P 6 winding or" relay 53, to ground. The closing of this circuit will operate relays 21 and 58. The operation of relay 21 will hold open at its armature and break contact the previ ously traced circuit through the lower wind-- ing of relay 17, thereby deenergizing relay 1?. The deenergization of relay 1? will allow the formerly traced circuit through relay 14 to be completed, and will thus cause the lamp 15 to light, thereby informing the operator that a connection has been made by the trunk. The operation of relay 53 closes the following circuit: from ground and battery, winding of relay 56, conductors 59 and 60, contact and armature of relay 53, conductor 55, interrupter 5e, to ground. Ci closing of this circuit energizes relay 5 1 thereby closing the following circuit: from ground, conductor 61, conductor 71, contact and armature of relay 56, conductor 72, ring contacts of jack J and plug P ring conductor of trunk a, right hand lower winding of transformer 16, winding of relay 2b to battery and ground. The closing of this circuit will operate relay 20, thereby closing the following circuit: from ground and bat tery, conductor 95, upper winding of 17, conductor 86, contact and armature relay 20, conductor 87, lower winding oi relay 17, conductor 88, contact and armature of relay 18, to ground. The closing of this circuit energizes relay 17 which pulls up its armatures and opens at contact points 89 and 90 the circuit previously traced from batter 7 19, through the winding of relay 1%, thereby deenergizing relay 1%, which dot nergization in turn causes the extinguishment of the signal lamp 15. The operation of relay 17 also closes the following locking circuit for relay 18: from ground and battery, lower winding of relay 18, conductor 85, contact and armature of relay 17, to ground. As the previously traced circuit about the winding of relay 56 includes the interrupting apparatus 54, the relay 56 will be caused to function intermittently Accordingly the previously traced circuit closed upon the energization of relay 56 about the relay 20 will be continuously opened and closec, thereby causing relay 20 to operate intermittently.- This in turn will cause the relay 1? to act intermittently, thereby continuously opening and closing the previously traced circuit from battery 19, through the winding of relay 14;. This will cause the relay 1e to act intermittently, thereby causing the supervisory signal lamp 15 to flash continuously, thus informing the operator of the busy condition of the called line. As the operation would be substantially as described it the trunk 4 were connected with any of the other jacks of the busy back circuit 51, a further description of the operation thereof will be omitted. The toll switching trunk a may also be used with the other forms of busy back circuits, such as illustrated in Figs. 3 and at. As the details of the operation of the arrangements shown in Figs. 3 and 4- have already been described with respect to the local trunk circuit f2, and as their operation would be substantially similar to that already described when used with the toll switching trunk 1, a further description of the operation thereof will be omitted.

While the invention has been disclosed as embodied in certain specific arrangements which have been deemed desirable, it is understood that it is capable of embodiment in many and widely varied forms without departin from the spirit of the invention as definec in the appended claims.

lVhat claimed is:

1. In a telephone system, a cord circuit including a supervisory signal, a trunk circult, means in said trunk for controlling said supervisory signal, a busy back circuit including a plurality of switching terminals, means to associate said trunk with one of said terminals, circuits individual to each of said switching terminals and adapted to control said means in said trunk, and means individual to each of said circuits for intermittently opening and closing said circuits.

2.111 a telephone system, cord circuits adapted for local calls, cord circuits adapted for long distance calls, supervisory signals in said cord circuits, trunk circuits adapted for use with said local cord circuits, trunl: circuits adapted for use with said long dis tance cord ircuits, means in said trunk circuits for controlling said supervisory signals, a busy back circuit including a plurality switching terminals, means to associate said trunks with said terminals, circuits ind'vidual to each of said switching terminals and adapted to control said means in said trunks, and means individual to each of said circuits for intermittently opening and closing said circuits' 3. A trunk circuit including a source of current and responsive means associated with the ring conductor thereof, a circuit including a plurality of switching terminals, means to associate said trunk with one of said terminals, means individual to each of said terminals for applying ground to the conductors associated with the ring contacts of said terminals, and means for intermittently operating said last mentioned means.

A busy back circuit including a pinrality of jacks, conductors associated with the ring contacts of said jacks, means responsive upon the association of a trunk circuit with one of said jacks for applying ground to all of said ring conductors, and means individual to said ring conductors for disconnecting said ground.

5. A trunk circuit including responsive means, a busy back circuit including a pluralitv of switching terminals, means to associate said trunk with any of said terminals, individual means associated with each of said terminals and responding when said trunk is associated therewith for operating said responsive means, and means for intermittently operating said individual means.

6. A trunli circuit including responsive means, a busy back circuit including a plurality of jacks, means to associate said trunk with any of said jacks, a relay associated with the sleeve conductors of all or said jacks and responding whenever said trunk is associated with one of said jacks, means controlled by said relay and individual to each of said jacks for operating said responsive means.

7. A trunk circuit :including responsive means, a busy back circuit including a plurality of switching terminals, means to associate said trunk with any of said terminals, individual means associated with each of said trunk is associated therewith for operating said responsive tently operating means for impressing a current of audible frequency on said individual means.

8. A trunk circuit including responsive means, a busy back circuit including a plurality of switching terminals, means to associate said trunk with one of said terminals, circuits individual to each oi' said switching terminals and adapted to control said responsive means, means individual to each of said circuits for intermittently opening and closing said circuits, audible frequency, and means to impress current from said source on said individual circuits.

In testimony whereof I have signed my name to this specification this 31st day of March, 1919. 7

JOHN F. TOOMEY.

terminals ,and responding when said means, means for intermit said individual means, and,

a source or current of V 

